In a transmissive liquid crystal display device, power consumption of a backlight largely affects power consumption of the whole of the liquid crystal display device, and therefore, reduction of light loss within a panel is important for reduction of power consumption. Loss of light within a panel is caused by light refraction in an interlayer insulating film, light absorption in a color filter, or the like. In particular, the light loss is large in principle in a color filter in which light absorption by a pigment is used to extract light having a predetermined range of wavelengths from white light. As a matter of fact, 70% or more of the energy of light from the backlight is absorbed by the color filter. As described above, the color filter hinders reduction in power consumption of the liquid crystal display device.
To avoid the problem of loss of light by the color filter, a field sequential driving (FS driving) is effective. The FS driving is a driving method for displaying a color image by sequentially lighting a plurality of light sources whose hues are different from each other. It is not necessary to use a color filter in the FS driving, which leads to reduction in light loss within a panel, so that the transmittivity of the panel can be improved. Accordingly, the use efficiency of light from the backlight can be improved and power consumption of the whole of the liquid crystal display device can be reduced. Further, according to the FS driving, an image for each color can be displayed per pixel, so that image display with high definition can be performed.
Disclosed in Patent Document 1 is a liquid crystal display device in which the displaying mode is switched between a color-image display using a field sequential displaying mode in the normal case and a monochrome display in the case where the image is a text or the like.